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  • The return value should be a list but doesn't return as expected?! - Python newbie

    - by user1432941
    Hi this must be a very simple solution that has eluded me this last hour. I've tried to build this test function where the return value of the test_cases list should match the values in the test_case_answers list but for some reason, test case 1 and test case 2 fail. When i print the return values for the test cases they return the correct answers, but for some reason test case 1 and test case 2 return False. Thanks for your help! import math test_cases = [1, 9, -3] test_case_answers = [1, 3, 0] def custom_sqrt(num): for i in range(len(test_cases)): if test_cases[i] >= 0: return math.sqrt(test_cases[i]) else: return 0 for i in range(len(test_cases)): if custom_sqrt(test_cases[i]) != test_case_answers[i]: print "Test Case #", i, "failed!" custom_sqrt(test_cases)

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  • Returning a list in this recursive coi function in python.

    - by Nate
    Hello. I'm having trouble getting my list to return in my code. Instead of returning the list, it keeps returning None, but if I replace the return with print in the elif statement, it prints the list just fine. How can I repair this? def makeChange2(amount, coinDenomination, listofcoins = None): #makes a list of coins from an amount given by using a greedy algorithm coinDenomination.sort() #reverse the list to make the largest position 0 at all times coinDenomination.reverse() #assigns list if listofcoins is None: listofcoins = [] if amount >= coinDenomination[0]: listofcoins = listofcoins + [coinDenomination[0]] makeChange2((amount - coinDenomination[0]), coinDenomination, listofcoins) elif amount == 0: return listofcoins else: makeChange2(amount, coinDenomination[1:], listofcoins)

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  • Is a python dictionary the best data structure to solve this problem?

    - by mikip
    Hi I have a number of processes running which are controlled by remote clients. A tcp server controls access to these processes, only one client per process. The processes are given an id number in the range of 0 - n-1. Were 'n' is the number of processes. I use a dictionary to map this id to the client sockets file descriptor. On startup I populate the dictionary with the ids as keys and socket fd of 'None' for the values, i.e no clients and all pocesses are available When a client connects, I map the id to the sockets fd. When a client disconnects I set the value for this id to None, i.e. process is available. So everytime a client connects I have to check each entry in the dictionary for a process which has a socket fd entry of None. If there are then the client is allowed to connect. This solution does not seem very elegant, are there other data structures which would be more suitable for solving this? Thanks

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  • program received signal SIGABRT (xcode)

    - by manish1990
    #import <UIKit/UIKit.h> @interface tableview : UIViewController<UITableViewDataSource> { NSArray *listOfItems; } @property(nonatomic,retain) NSArray *listOfItems; @end #import "tableview.h" @implementation tableview @synthesize listOfItems; - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier ]autorelease]; } //NSString *cellValue = [listOfItems objectAtIndex:indexPath.row]; cell.textLabel.text = [listOfItems objectAtIndex:indexPath.row]; return cell; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return 3; } - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { // Custom initialization } return self; } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } #pragma mark - View lifecycle - (void)viewDidLoad { listOfItems = [[NSArray alloc] initWithObjects:@"first",@"second",@"third", nil]; //listOfItems = [[NSMutableArray alloc]init]; // [listOfItems addObject:@"first"]; //[listOfItems addObject:@"second"]; [super viewDidLoad]; // Do any additional setup after loading the view from its nib. } -(void)dealloc { [listOfItems release]; [super dealloc]; } @end GNU gdb 6.3.50-20050815 (Apple version gdb-1708) (Mon Aug 15 16:03:10 UTC 2011) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-apple-darwin".sharedlibrary apply-load-rules all Attaching to process 438. 2012-04-27 13:33:23.276 tableview test[438:207] -[UIView tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x6855500 2012-04-27 13:33:23.362 tableview test[438:207] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIView tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x6855500' * First throw call stack: (0x13bb052 0x154cd0a 0x13bcced 0x1321f00 0x1321ce2 0x1ecf2b 0x1ef722 0x9f7c7 0x9f2c1 0xa228c 0xa6783 0x51322 0x13bce72 0x1d6592d 0x1d6f827 0x1cf5fa7 0x1cf7ea6 0x1d8330c 0x23530 0x138f9ce 0x1326670 0x12f24f6 0x12f1db4 0x12f1ccb 0x12a4879 0x12a493e 0x12a9b 0x2282 0x21f5) terminate called throwing an exceptionCurrent language: auto; currently objective-c (gdb)

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  • lambda vs. operator.attrGetter('xxx') as sort key in Python

    - by Paul McGuire
    I am looking at some code that has a lot of sort calls using comparison functions, and it seems like it should be using key functions. If you were to change seq.sort(lambda x,y: cmp(x.xxx, y.xxx)), which is preferable: seq.sort(key=operator.attrgetter('xxx')) or: seq.sort(key=lambda a:a.xxx) I would also be interested in comments on the merits of making changes to existing code that works.

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  • How to display a page in my browser with python code that is run locally on my computer with "GAE" S

    - by brilliant
    When I run this code on my computer with the help of "Google App Engine SDK", it displays (in my browser) the HTML code of the Google home page: from google.appengine.api import urlfetch url = "http://www.google.com/" result = urlfetch.fetch(url) print result.content How can I make it display the page itself? I mean I want to see that page in my browser the way it would normally be seen by any user of the internet.

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  • Python - Is a dictionary slow to find frequency of each character?

    - by psihodelia
    I am trying to find a frequency of each symbol in any given text using an algorithm of O(n) complexity. My algorithm looks like: s = len(text) P = 1.0/s freqs = {} for char in text: try: freqs[char]+=P except: freqs[char]=P but I doubt that this dictionary-method is fast enough, because it depends on the underlying implementation of the dictionary methods. Is this the fastest method?

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  • Python - 2 Questions: Editing a variable in a function and changing the order of if else statements

    - by Eric
    First of all, I should explain what I'm trying to do first. I'm creating a dungeon crawler-like game, and I'm trying to program the movement of computer characters/monsters in the map. The map is basically a Cartesian coordinate grid. The locations of characters are represented by tuples of the x and y values, (x,y). The game works by turns, and in a turn a character can only move up, down, left or right 1 space. I'm creating a very simple movement system where the character will simply make decisions to move on a turn by turn basis. Essentially a 'forgetful' movement system. A basic flow chart of what I'm intending to do: Find direction towards destination Make a priority list of movements to be done using the direction eg.('r','u','d','l') means it would try to move right first, then up, then down, then left. Try each of the possibilities following the priority order. If the first movement fails (blocked by obstacle etc.), then it would successively try the movements until the first one that is successful, then it would stop. At step 3, the way I'm trying to do it is like this: def move(direction,location): try: -snip- # Tries to move, raises the exception Movementerror if cannot move in the direction return 1 # Indicates movement successful except Movementerror: return 0 # Indicates movement unsuccessful (thus character has not moved yet) prioritylist = ('r','u','d','l') if move('r',location): pass elif move('u',location): pass elif move('d',location): pass elif move('l',location): pass else: pass In the if/else block, the program would try the first movement on the priority on the priority list. At the move function, the character would try to move. If the character is not blocked and does move, it returns 1, leading to the pass where it would stop. If the character is blocked, it returns 0, then it tries the next movement. However, this results in 2 problems: How do I edit a variable passed into a function inside the function itself, while returning if the edit is successful? I have been told that you can't edit a variable inside a function as it won't really change the value of the variable, it just makes the variable inside the function refer to something else while the original variable remain unchanged. So, the solution is to return the value and then assign the variable to the returned value. However, I want it to return another value indicating if this edit is successful, so I want to edit this variable inside the function itself. How do I do so? How do I change the order of the if/else statements to follow the order of the priority list? It needs to be able to change during runtime as the priority list can change resulting in a different order of movement to try.

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  • How to assure applying order of function decorators in Python?

    - by Satoru.Logic
    Some decorators should only be used in the outermost layer. A decorator that augments the original function and add a configure parameter is one example. from functools import wraps def special_case(f): @wraps(f) def _(a, b, config_x=False): if config_x: print "Special case here" return return f(a, b) How can I avoid decorators like this getting decorated by another decorator? EDIT It is really disgusting to let everyone trying to apply a new decorator worry about the application order. So, is it possible to avoid this kind of situation? Is it possible to add a config option without introducing a new parameter?

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  • Are python list comprehensions always a good programming practice?

    - by dln385
    To make the question clear, I'll use a specific example. I have a list of college courses, and each course has a few fields (all of which are strings). The user gives me a string of search terms, and I return a list of courses that match all of the search terms. This can be done in a single list comprehension or a few nested for loops. Here's the implementation. First, the Course class: class Course: def __init__(self, date, title, instructor, ID, description, instructorDescription, *args): self.date = date self.title = title self.instructor = instructor self.ID = ID self.description = description self.instructorDescription = instructorDescription self.misc = args Every field is a string, except misc, which is a list of strings. Here's the search as a single list comprehension. courses is the list of courses, and query is the string of search terms, for example "history project". def searchCourses(courses, query): terms = query.lower().strip().split() return tuple(course for course in courses if all( term in course.date.lower() or term in course.title.lower() or term in course.instructor.lower() or term in course.ID.lower() or term in course.description.lower() or term in course.instructorDescription.lower() or any(term in item.lower() for item in course.misc) for term in terms)) You'll notice that a complex list comprehension is difficult to read. I implemented the same logic as nested for loops, and created this alternative: def searchCourses2(courses, query): terms = query.lower().strip().split() results = [] for course in courses: for term in terms: if (term in course.date.lower() or term in course.title.lower() or term in course.instructor.lower() or term in course.ID.lower() or term in course.description.lower() or term in course.instructorDescription.lower()): break for item in course.misc: if term in item.lower(): break else: continue break else: continue results.append(course) return tuple(results) That logic can be hard to follow too. I have verified that both methods return the correct results. Both methods are nearly equivalent in speed, except in some cases. I ran some tests with timeit, and found that the former is three times faster when the user searches for multiple uncommon terms, while the latter is three times faster when the user searches for multiple common terms. Still, this is not a big enough difference to make me worry. So my question is this: which is better? Are list comprehensions always the way to go, or should complicated statements be handled with nested for loops? Or is there a better solution altogether?

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  • Gtk_entry mouse click signal

    - by h4rp0
    Hi, I want to do a g_signal_connect to capture a mouse click in a gtk_entry widget. Something like this: entry = gtk_entry_new ( ); gtk_box_pack_end ( GTK_BOX ( hBox ), entry, TRUE, TRUE, 1 ); gtk_widget_show ( entry ); // This is the one I'm not sure about g_signal_connect ( GTK_OBJECT ( entry ), "????????????", GTK_SIGNAL_FUNC ( EntryClicked ), entry ); I just can't seem to find it in the gtk documentation. I've tried using the "focus-in-event", but it is not working as I spect. Thanks for the assistance.

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  • Python raises a KeyError (for an out of dictionary key) even though the key IS in the dictionary

    - by ignorantslut
    I'm getting a KeyError for an out of dictionary key, even though I know the key IS in fact in the dictionary. Any ideas as to what might be causing this? print G.keys() returns the following: ['24', '25', '20', '21', '22', '23', '1', '3', '2', '5', '4', '7', '6', '9', '8', '11', '10', '13', '12', '15', '14', '17', '16', '19', '18'] but when I try to access a value in the dictionary on the next line of code... for w in G[v]: #note that in this example, v = 17 I get the following error message: KeyError: 17 Any help, tips, or advice are all appreciated. Thanks.

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  • Python - Find where in string regex match was found?

    - by nb
    I'm currently using regular expressions to search through RSS feeds to find if certain words and phrases are mentioned, and would then like to extract the text on either side of the match as well. For example: String = "This is an example sentence, it is for demonstration only" re.search("is", String) I'd like to know where the is was found so that I can extract and output something like this: 1 match found: "This is an example sentence" I know that it would be easy to do with splits, but I'd need to know what the index of first character of the match was in the string, which I don't know how to find

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  • How to select random image of specific size using Django / Python?

    - by Jonathan
    I've been using this little snippet to select random images. However I would like to change it to select only images of a certain size. I'm running into trouble checking against image size. If I use get_image_dimensions() I need to use a conditional statement, which then requires that I allow exceptions. So, I guess I need some pointers on just limiting by image dimensions. Thanks. import os import random import posixpath from django import template from django.conf import settings register = template.Library() def is_image_file(filename): """Does `filename` appear to be an image file?""" img_types = [".jpg", ".jpeg", ".png", ".gif"] ext = os.path.splitext(filename)[1] return ext in img_types @register.simple_tag def random_image(path): """ Select a random image file from the provided directory and return its href. `path` should be relative to MEDIA_ROOT. Usage: <img src='{% random_image "images/whatever/" %}'> """ fullpath = os.path.join(settings.MEDIA_ROOT, path) filenames = [f for f in os.listdir(fullpath) if is_image_file(f)] pick = random.choice(filenames) return posixpath.join(settings.MEDIA_URL, path, pick)

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